| Abstract: | The following is the abstract of the article discussed inthe subsequent letter:Yuan, Huichin, Edward P. Ingenito, and BélaSuki. Dynamic properties of lung parenchyma: mechanicalcontributions of fiber network and interstitial cells. J. Appl.Physiol. 83(5): 1420-1431, 1997. We investigated thecontributions of the connective tissue fiber network and interstitialcells to parenchymal mechanics in a surfactant-free system. In eightstrips of uniform dimension from guinea pig lung, we assessed thestorage (G') and loss (G") moduli by using pseudo-random lengthoscillations containing a specially designed set of seven frequenciesfrom 0.07 to 2.4 Hz at baseline, during methacholine (MCh) challenge,and after death of the interstitial cells. Measurements were made atmean forces of 0.5 and 1 g and strain amplitudes of 5, 10, and 15% andwere repeated 12 h later in the same, but nonviable samples. Theresults were interpreted using a linear viscoelastic modelincorporating both tissue damping (G) and stiffness (H). The G' and G"increased linearly with the logarithm of frequency, and both G and Hshowed negative strain amplitude and positive mean force dependence. After MCh challenge, the G' and G" spectra were elevated uniformly, andG and H increased by <15%. Tissue stiffness, strain amplitude, andmean force dependence were virtually identical in the viable andnonviable samples. The G and hence energy dissipation were ~10%smaller in the nonviable samples due to absence of actin-myosin cross-bridge cycling. We conclude that the connective tissue network may also dominate parenchymal mechanics in the intact lung, which canbe influenced by the tone or contraction of interstitial cells. |
